The M protein is dispensable for maturation of streptococcal cysteine protease SpeB.
The M protein is dispensable for maturation of streptococcal cysteine protease SpeB.
复制标题
M 蛋白对于链球菌半胱氨酸蛋白酶 SpeB 的成熟是可有可无的。
DOI：
10.1128/iai.73.2.859-864.2005
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发表时间：
2005
期刊：
影响因子：
--
通讯作者：
Cleary,PPatrick
中科院分区：
文献类型：
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作者：
Zimmerlein,Bjorn;Park,Hae-Sun;Li,Shaoying;Podbielski,Andreas;Cleary,PPatrick
链球菌热原性外毒素 B (SpeB) 是 A 族链球菌 (GAS) 的重要毒力因子，具有半胱氨酸蛋白酶活性。 SpeB 成熟为蛋白水解活性形式取决于细胞壁锚定的 M1 蛋白，即 GAS 的主要表面蛋白（M. Collin 和 A. Olsén，Mol. Microbiol.36：1306-1318，2000）。 Collin 和 Olsén 表明，表达截短的 M 蛋白的突变 GAS 菌株会分泌一种构象不同的未加工 SpeB，不具有蛋白水解活性。或者，我们假设截短的 M 蛋白可能会干扰这种分泌型蛋白酶的加工，因此我们测试了基因定义的突变株中的半胱氨酸蛋白酶活性，这些突变株要么不表达 M 蛋白，要么表达膜锚定的 M 蛋白，并框内删除 AB 重复区域。通过底物苯甲酰基-Pro-Phe-Arg-p-硝基苯胺盐酸盐的裂解测量SpeB活性，结果表明两种突变体培养物上清液中的蛋白水解活性与野生型菌株相似。此外，培养物上清液的蛋白质印迹分析表明，SpeB 表达和加工成成熟形式不受任一缺失突变的影响。因此，我们得出结论，M 蛋白不是链球菌半胱氨酸蛋白酶 SpeB 成熟所必需的。
The streptococcal pyrogenic exotoxin B (SpeB) is an important virulence factor of group A streptococci (GAS) with cysteine protease activity. Maturation of SpeB to a proteolytically active form was suggested to be dependent on cell-wall-anchored M1 protein, the major surface protein of GAS (M. Collin and A. Olsén, Mol. Microbiol.36:1306-1318, 2000). Collin and Olsén showed that mutant GAS strains expressing truncated M protein secrete a conformationally different form of unprocessed SpeB with no proteolytic activity. Alternatively, we hypothesized that a truncated M protein may interfere with processing of this secreted protease, and therefore we tested cysteine protease activity in genetically defined mutant strains that express either no M protein or membrane-anchored M protein with an in-frame deletion of the AB repeat region. Measurements of SpeB activity by cleavage of a substraten-benzoyl-Pro-Phe-Arg-p-nitroanilide hydrochloride showed that the proteolytic activities in culture supernatants of both mutants were similar to those from the wild-type strain. In addition, Western blot analysis of culture supernatants showed that SpeB expression and processing to a mature form was unaffected by either deletion mutation. Therefore, we conclude that M protein is not required for maturation of the streptococcal cysteine protease SpeB.